Geosynchronous Earth Orbiting (GEO) and/or Low Earth Orbiting (LEO) satellites are often deployed in satellite constellations. LEO satellites may have coverage areas that only covers a small area on the ground at a given time. The area covered moves as the satellite travels at a high angular velocity. A high angular velocity is needed in order to maintain the LEO satellite in orbit. Many LEO satellites are needed to maintain continuous coverage over an area. LEO satellites contrast with GEO satellites, where a single GEO satellite, moving at the same angular velocity as the rotation of the earth's surface, may provide permanent coverage over a large area.
Examples of satellite constellations include the Global Positioning System (GPS), Galileo and GLONASS constellations for navigation and geodesy; the Iridium and Globalstar satellites for telephony services; the Disaster Monitoring Constellation and RapidEye for remote sensing; the Orbcomm satellites for messaging service; the Russian elliptic orbit Molniya and Tundra constellations; and the Cospas-Sarsat search and rescue satellites.
Broadband applications may benefit from low-latency communications, so LEO satellite constellations provide an advantage over a geostationary satellite. The minimum theoretical latency for a GEO satellite is about 250 milliseconds, compared to only a few milliseconds for a LEO satellite. A LEO satellite constellation can also provide more system capacity by frequency reuse across its coverage, with spot beam frequency use being analogous to the frequency reuse of cellular base station radio towers. However, LEO satellites suffer from a scan problem. When a user wishes to initiate communication, it may be minutes or hours before a LEO satellite is above the horizon and can begin a communication session. Similar issues face other types of non-GEO satellites.
The U.S. Federal Communications Commission (FCC) requires that communication over a GEO satellite should operate at a low power density. Consequently, a satellite signal received at an arbitrary point on the ground, with an antenna pointing in an arbitrary direction, may typically be weak and may not be distinguishable from noise. Downlink signals from LEO or other non-GEO satellites suffer from similar power density limitations and may also need directional precision in acquiring their signals at ground-based stations.
Hence, to receive signals or messages from a satellite, a receiver must generally know the approximate location of a satellite and point its antenna in the direction of the satellite. By so doing, the receiver may then be able to receive a downlink signal (i.e., from satellite to ground), which may then be processed and may be successfully demodulated.
As described above, the process of detecting a satellite signal starts with knowing the approximate exact location of the satellite in the sky and pointing the antenna of the receiver towards the satellite. Applications such as Satellite AR by Analytical Graphics, Inc. (play.google.com/store/apps/details?id=com.agi.android.augmentedreality&hl=en), DishPointer Augmented Reality (www.dishpointer.com/2009/augmented-reality-satellite-finder), and others may facilitate pointing a hand held device such as, e.g., a mobile phone, tablet computer, or a Higher Ground LLC SatPaq™ mobile unit, to point towards a specific GEO satellite. Such applications are generally limited to GEO satellite uses because the position of a GEO satellite is known, based on its geosynchronous orbit.
Existing applications rely on sensors such as a compass, tilt sensors, etc. to direct the user of the augmented reality to point the device towards a specific satellite. These sensors can be either built in the device such as sensors built in a mobile phone, or external sensors that are attached or otherwise associated with the AR device. In either case, these sensors may have limited accuracy that may decrease the precision with which the device is able to be pointed at the intended satellite. This, in turn, may result in a decrease in power of the received signal from the satellite and, in general, reduce the ability of the device to acquire a satellite.